The present invention relates to sighting devices for aligning firearms, geodesic instruments, such as transits, and the like, with a target, accurately and rapidly.
Sighting devices are known such as the pointer sights system which is commonly used for aiming firearms at a target situated at a medium or short distance. Sighting devices of this kind consist of a short rod or pointed projection, or front sight, and of a horizontal, vertically adjustable metallic part with a V-groove, or rear sight, which are both mounted on the weapon or other instrument so that the user sights through the rear sight onto the front sight, and aligns the two sights with the target. In this manner, the eye of the user must be aligned with the rear sight, the front sight and the target, all situated exactly on a single straight line, the so-called target line, or alignment of the instrument with the target is not possible. Such exact alignment of the eye with the target line takes a certain amount of time, proper concentration and adequate skill on the part of a marksman. For this reason, conventional pointer sights systems cannot be used with adequate accuracy by the average person. In addition, accuracy is hampered because the eye is focused to the far-away target, such that the rear and the front sights are seen as out-of-focus blurred images. This disadvantage of pointer sights systems may be reduced by placing the sights as far away from the eye as possible, which can be done only with relatively long firearms, or other devices having a long sight line. In addition, the distance separating the rear and the front sights must be as wide as possible for the sake of better accuracy. This is in contradiction with the requirement of a long distance from the rear sight to the eye, and it is limited by the design length of the firearm or other device. Finally, another disadvantage associated with pointer sights systems is that only the upper half of the target is visible since the lower half of the target is masked by the rear and front sights. This results in a considerable reduction of the overall visibility of the target.
Another well-known sighting device is a modification of the pointer system which is sometimes known under the name "Diopter." In such modification, the rear sight is replaced by an apertured wall or mask which is disposed proximate the eye of the person airming at the target. The tip of the front sight is viewed through this aperture and aligned with the target. In this manner, an improved accuracy may be achieved as compared to the conventional pointer sights system, because the closeness of the aperture to the eye provides a longer distance to the front sight. However, since the aperture must have a very small diameter, for reasons of accuracy, the field of vision through the aperture is considerably restricted, which in turn considerably reduces the visibility of the target.
Sighting devices of higher accuracy, of the telescope type, often called telescopic sights are also known. At the point of view of their optical design, telescopic sights are terrestrial telescopes which, in addition to the objective forming an intermediate image plane and of the ocular, require an additional lens which, through a further projection of the intermediate plane image, effectuates a reconstruction of the image. In one of the two intermediate images, that is between the objective lens and the additional lens, or between the additional lens and the ocular, an adjustable target mark, called a graduated plate, is inserted which is provided with a reticle which is seen through the ocular in the same plane as the target plane. Consequently, the optical characteristics of the ocular, or eyepiece, must be calculated such as to provide an exit pupil situated as far back as possible in order to keep the distance between the eye and the telescopic sight as large as feasible in order to avoid eye injuries due to weapons having a heavy recoil. Telescopic sights have generally a 6.times. magnification and are thus particularly suited for sighting far-away targets. One of their disadvantages, however, which is due to the substantial magnification, is that only a small section of the target is visible. Thus, the field of view is severly restricted, which is even more important when the target is at a medium or short distance, such that telescopic sights are not particularly well suited for aiming at targets at such medium or short distance. In addition, telescopic sights, due to their optical system design, are expensive and have a barrel which is quite long because of the extended image reversal optical system. An additional disadvantage of telescopic sights is that the black reticle on the graduated plate can only be seen with great difficulty when superimposed on dark targets. Moreover, because of the high magnification and the correspondingly magnified errors due to misadjustment, telescopic sights must be repeatedly re-adjusted with precision.
In addition to the already mentioned disadvantages, the prior art devices described hereinbefore have an important common deficiency. In addition to the requirement that the weapon or other instrument be correctly aligned with the target, it is necessary for the viewer to bring his eyes into the target line with the greatest precision possible in order to judge good aiming. Faulty alignment of the eye is often judged as a sighting error, while the sighting system should not be blamed, which obviously does not mean that sighting errors do not indeed occur.
The mentioned disadvantages due to misalignment of the eye with the target line does not, however, exist with another prior art sighting device disclosed in German Pat. No. 269,447. In this prior art sighting device, the lens barrel which encloses the optical system is so designed that the semi-transparent mirror surface reflecting the target mark is disposed at a considerable distance from the convex optically effective surface in the interior of the lens barrel. The mirror surface is itself curved, its curvature being different from that of the two optically effective surfaces. Because the semi-transparent mirror surface is disposed within the interior of the lens housing, the lens housing is divided into two sections which, for defining this mirror surface as a glass-air surface, are simply joined together by means of an adhesive so as to define the mirror surface, or they can be fused together.
Because of the arrangement consisting of the semi-transparent mirror surface being disposed within the lens itself, there results a complication of the computing of the lens characteristics, resulting in turn in excessive manufacturing costs. Such disadvantage is further compounded because such sighting devices have applications not only in firearms but in photographic equipment, and those devices are manufactured in mass production for which even a slight increase in manufacturing costs has deep economic ramifications.
The present invention accomplishes the results of providing a simple and effective optical sighting device which in addition to being suitable for long distances is also suitable for medium or short distances, which does not present the disadvantages of the prior art sighting devices, and which is also very favorably priced as compared to the cost of manufacturing the prior art sighting devices.
Those objects are accomplished by the present invention as a result of providing an optical sighting device comprising a single lens massive body having one of its optically effective end surfaces provided with a partially transparent and partially reflective coating.
Although the optical sighting device of the present invention is of simple design, it still provides accurate aiming. The whole optical system consists of a single body of glass or other light transmissive material, the single body being provided with opposite optically effective surfaces. The optical surfaces are preferably spherical or rotation-symmetrical, for the sake of simplified manufacturing, but they can, nevertheless, be also developed as aspherical surfaces. A first effective surface, which is optically convex, concentrates the light rays in the fashion of an objective lens for forming an image, and the second, concave, optically effective surface deflects the light prior to formation of the image into infinity, in the same manner as an eyepiece, such as to fulfill the operation of telescope optical elements. The optical sighting device of the invention is therefore a telescope of the simplest design, which can be manufactured at the most modest costs and which is, so to speak, a simplified type of the Galileo, or Dutch-type, telescope which, as is well known, delivers a terrestrial or erect image. Thus, the present invention does not require an additional image reversing lens system. Due to the relatively low magnification of the telescope type sighting system of the invention, the human eye naturally and easily adjusts for varying distances, such that special precise focusing elements are not necessary. In addition, possible eventual misadjustments have less effect upon the human eye in view of the low magnification of the telescope. As a result of the reduced magnification, an added advantage is that the field of view under which the target is sighted is relatively wide, which results in being able to rapidly locate the target and aim at the target. Finally, the sighting device of the invention makes it possible, as long as the optically effective surfaces are of good quality, to view in a single plane the target and the target mark.
Compared to the device disclosed in German Pat. No. 269,447, the sighting device of the invention, due to using a solid mass of glass or other material for the optical system from effective optical surface to effective optical surface in which the two frontal surfaces are arranged to have respectively the target mark and a semi-transparent coating, presents the advantage of considerably simplifying the calculation of the lens system and of reducing the cost of manufacturing. Also, by eliminating the requirement of separate, curved semi-transparent mirror surfaces on the interior of the lens body, there results a reduction of possible sources of error either in calculation or in production.
Because of the particular advantageous arrangment of the optical system of the invention, the lens frontal surfaces have a curvature of such kind and are situated at an appropriate distance from each other with the result that the light rays reflected by the target mark upon reflection upon the first surface are reflected in such a way that they merge with the rays originating from the target which are refracted by the first optical surface.
As is known, Galileo type telescopes do not provide an intermediate image with the aid of which a target mark could be projected into infinity. However, by the arrangement provided by the present invention, this is obtained in an especially simple way such that the second optically effective surface, besides its light refracting function, serves simultaneously as the support for the target mark, made of reflective material, and that the optically effective first surface is made semi-reflective by means of an appropriate coating. In such manner, the surface acts as a reflective surface at the same time as acting as a refractive surface for the light rays. The two optically effective surfaces thus have a double function which considerably reduces the number of optically effective components. By choosing an appropriate distance between the two surfaces, i.e., by choosing an appropriate actual thickness of the lens body, it is possible to have the target mark projected to infinity simultaneously with obtaining the optical telescope effect, such that the viewer sees the target and the target mark clearly in a single plane. Fulfilling both requirements is possible for every light refracting medium at a certain magnification, for example, for crown glass the magnification factor is 1.26.times.. In this manner, the target mark is observed with a magnification corresponding to an ordinary magnifying glass, whereby the focal length of the magnifying glass results from the predetermined dimensions between the reflecting first surface and the light defracting second surface, and is thus dependent upon the actual length of the lens mass. In the above mentioned example of using crown glass, with a thickness of glass of 30mm between the first and second surfaces a magnifying glass magnification of 10.5.times. results for the target mark. The target mark, or reticle, therefore needs to be provided on the second optically effective surface only in a relatively small size. Consequently, the target mark causes very little interference with sighting through the second surface, and therefore provides only a negligible loss of brightness since it is of relatively small overall size and the lines forming the reticle, or other target mark, are only a few hundredths of a millimeter in width. Finally, the reflected target mark appears to be bright relative to the light surrounding the target, which considerably improves the visibility of dark targets especially at night or at dusk.
Another advantage of the present invention is that the two optically effective surfaces have such curvature and are situated at a distance from each other such that the diameter of the exit pupil is larger than that of the pupil of the human eye. For practical purposes, the diameter of the exit pupil is in the range of 15 to 25mm, preferably 20mm.
The particularly wide exit pupil obtained by the present invention which results from, among other factors, the relatively small telescope magnification, provides very important advantages in an optical sight. Since the light originating from the target placed at infinity, after passage through the second optically effective surface emerges over the full diameter of the exit pupil parallel to the optical axis, the human eye does not have to be positioned with precision, either radially or axially. It is sufficient if the eye is located within the bundle of parallel rays emerging through the wide exit pupil. Thus, precise alignment of the eye with the target line is not required. In this respect, particularly important advantages are provided by the present invention as compared with prior art sighting devices. Aiming is rendered considerably easier and, most of all, requiring much less time and concentration. This is particularly important for firearms since it is evident that such a simplified, rapid and accurate aiming procedure, in view of the great visibility of the target as provided by the invention, is of utmost importance, especially for a chance for survival in man-to-man combat. It has also advantages for other applications, such as for geodesic transits, such advantages taking place during the aiming procedure.
In order to compensate for spherical aberration within the lens mass itself, according to the present invention, the distance between the first and second optically effective surfaces is preferably determined such that the deviation angle of any single ray over the entire diameter of the exit pupil at least at three points, especially at the optical axis and on two diametrically opposed points located at the outer limit of the exit pupil, is zero and negligibly small for any intermediary points. A relatively high precision in the parallelism of the light rays exiting through the exit pupil can be obtained with aspherical, or rotation symmetrical, optically effective surfaces. But it must be taken into consideration that obtaining aspherical surfaces with the inherent required precision desired involves correspondingly high accuracy in grinding the lens surfaces with resulting high cost in labor and production costs. Consequently, according to the present invention, spherical and optically effective lens surfaces are used which can be obtained with very high precision, but by much simpler methods than aspherical surfaces. Since the spherical surfaces, however, are optically accurate only proximate to the optical axis while showing increasing refraction errors proportionally to the distance from the optical axis toward the periphery of the lens system, increasing with the distance from the optical axis, such errors being both errors in deflection of the light beam as well as, more importantly yet, reflection errors, a corresponding correction becomes necessary. The correcting factors for the image producing errors, or aspherical aberrations, are preferably obtained by means of proper design. Consequently, the exact locations of the points of zero deviation over the diameter of the exit pupil are chosen such that the deviation errors between the zero points are smaller than the resolution factor of the human eye, as well as smaller than the scatter range, especially of hand firearms, and thus negligible. It should be also appreciated that the lens body, according to this invention, in the same manner than prescription eyeglasses, may show some chromatic aberrations which do not result in refraction.
An additional advantage of the present invention results from the fact that the lens body, preferably enclosed in a cylindrical housing, whether mounted at the rear of a firearm barrel, or in a geodesic instrument or the like, is spring mounted by means of one or several parallelly stacked flat leaf springs which are provided with an appropriate aperture along the optical axis of the lens system. Although the flat springs, as will be disclosed, provide a square aperture, it will be evident that they can be arranged such as to provide a circular aperture. The aperture provided by the mounting springs acts an an aperture or viewing window for the viewer through which the light rays emerge from the lens body towards the viewer. Consequently, when a circular aperture in the flat springs is provided, there results a circular viewing aperture or window.
The lens suspension springs are provided with mounting holes disposed two-by-two in separate planes and along axes crossing each other at a 90.degree. angle, with a pair of mounting holes in one plane for attachment to the lens body and another pair of mounting holes for attachment to a support frame ring in turn rigidly mounted on the firearm, the geodesic transit or the like. In this manner, a free floating connection is effected between the lens body housing and the support ring which permits motion of one element relative to the other within a range determined by the spring design, and which is similar in action to a Cardan suspension.
Pre-stressing, or deflecting, of the flat springs is provided by several adjustment screws threading into the lens body barrel. The other end of the adjusting screws abuts against the support ring. In this manner, the springs between the lens barrel and the support ring are pre-loaded and the adjusting screws, by preloading the springs and acting as abutment means, control the range of possible motion of the spring suspension between the lens body and the support ring.
This arrangement also permits to adjust the optical axis of the lens body in azimuth and in elevation relative to its axes of symmetry, such as to accurately position the optical axis relative to the operational axis of the firearm or other device. Three adjustment screws are provided which are arranged relative to each other such that they are located each at an apex of a right triangle whose perpendicular sides are parallel to the axes of symmetry. For adjustment of the lens body in azimuth or in elevation, the screws at each end of the hypotenuse of the triangle are used while the third screw remains fixed. Through appropriate tightening or loosening of one of the two screws on the hypotenuse of the triangle the lens body can be precisely swiveled in elevation or azimuth within the course of the springs. The third screw at the apex of the triangle has only a holding function.
It will also be appreciated that the adjustment screws, at the same time, serve to preload the flat springs in addition to adjusting the alignment of the optical axis of the lens system, in such manner that for preloading of the flat springs all the adjustment screws are equally tightened, and, for adjusting the optical axis of the lens system, only one screw is tightened or loosened, thus causing the lens body to swivel about the axis formed by the opposite short side of the right angle triangle.
According to a further aspect of the present invention, the adjustment screws are arranged so that the geometric center of the flat springs is located within the triangle defined by the adjustment screws. Since it can be assumed that all effective and resulting forces acting upon the flat springs are applied at the geometric center of the springs, or spring center of gravity, it results, as can be readily seen, that the arrangement according to the present invention of the adjustment screws relative to the spring center of gravity provides at all times a stable balance or equilibrium, while providing an adjustment arrangement for the lens body which remains undisturbed even if a considerable motion is encountered, such as will occur with firearms having a powerful recoil.
Safe functioning and protection from adverse conditions is provided to the sighting device according to the present invention by enclosing the lens body, with appropriate clearance, in a protective tubing attached firmly to the front end of the support ring, the protective tubing extending forwardly and projecting beyond the front end face of the lens body. The protective tubing protects the lens from damages and resulting misalignments. At the same time, the protective tubing serves to screen out unwanted light.
U.S. Pat. No. 2,968,099 discloses a protective tubing for a sighting device. In the arrangement disclosed, however, the tubing is simply slipped over the outer end of the sighting device, so that unfavorable external influences affecting the tubing can also affect the sighting mechanism. Furthermore, the protective tubing is costly to manufacture. By comparison, the simple tubing provided by the present invention is not attached to the lens body itself but to the front end of the stable sturdy support ring in such manner as to provide a clearance space between the periphery of the lens body and the internal surface of the tubing. It can thus be seen that the arrangement according to the present invention prevents any external shock or vibration affecting the protective tubing from, as a rule, being transmitted to the lens body, since the tubing is attached to the lens support ring with a clearance space between the lens body and the tubing interior. A rear cover cap, also providing an aperture window, can be attached to the rear portion of the support ring, which presents the added advantage of masking any unwanted light from the ocular or eyepiece portion of the lens.
A particular advantage of the optical sight of the present invention, which at the same time provides the desired protection from unwanted outside influences, is particularly well adapted for use with firearms in which the whole optical sighting assembly is mounted within a rear extension of the firearm carrying handle, such that the lens body is aligned within a recess in the carrying handle which is parallel to the barrel of the firearm. Since the carrying handles are designed quite sturdily in view of their function, they provide, without additional expenditure, an optimum means of protection for the optical sighting device of the invention.
From the German published application No. 1,924,606 and corresponding U.S. Pat. No. 3,642,341 it is basically known that an optical sighting device may be incorporated in the handle of a firearm. In that disclosure, however, the optical sighting unit is built into that part of the handle which is usually gripped by the hand, thus making it necessary for that part to be designed quite large in order to accomodate a sighting device of large diameter. This causes the carrying handle to be higher than otherwise necessary, which presents a basic disadvantage. On the other hand, in such arrangement the space available for accomodating the sighting device within the handle is automatically limited by the size of the grip of the fingers. This in turn results in a smaller exit pupil for the sighting device which is an important disadvantage when compared to the present invention. In contrast, in the arrangement of the present invention the optical sighting device is not mounted directly in the inside of the handgrip portion of the carrying handle but, rather, in a rear extension of the carrying handle, i.e., at the portion of the handle provided with an opening forming a grip for the fingers. Thus, a carrying handle of minimum height is provided. Since the opening accomodating the fingers can be designed sufficiently high, the diameter of the exit pupil according to the present invention can be arbitrarily chosen to meet any requirement.
A further advantage of the invention is to provide a mounting or frame ring which is rigidly attached to the rear extension of the firearm carrying handle such that the rear extension of the handle houses the lens body with appropriate clearance. This arrangement provides an advantageous suspension of the lens body within the rear extension of the handle.
Another advantage of the invention consists in the rear extension of the handle extending at its forward portion considerably over the front portion of the lens body. Thus the frontal extension provides a hood or visor keeping out unwanted light without requiring additional components.
A further advantage of the present invention resides in the rear aperture window cap which is attached to the rear end of the rear extension of the carrying handle thus likewise helping to screen out unwanted light.
Further advantages of the present invention will become apparent to those skilled in the art when the following description of the best modes contemplated for practicing the invention is read in conjunction with the accompanying drawing wherein like reference numerals relate to like and equivalent parts, and in which: